/*
 * Anything: A flexible and easy to use data structure that combines the 
 * characteristics of a list and a hashmap into one data structure.
 * 
 * Based on a paper by Peter Sommerlad and Marcel Rueedi on 
 * 'Do-it-yourself reflection' entered at EuroPLOP 1998.
 * 
 * This library was written completely from scratch and is based only 
 * in spirit on the original Java Anything implementation written by 
 * Andre Weinand/Marcel Rueedi in 1997/99 and enhanced by Stefan Tramm 
 * in 2006.
 * 
 * Copyright (c) 2008 Thomas Marti and others. All rights reserved.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *   http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package any.impl.util;

import java.util.prefs.*;

/**
 * Utility class that encodes and decodes byte arrays in Base64 representation.
 * Uses underlying functionality in the java.util.prefs package of the Java API.
 * Note that this is slightly different from RFC 2045; ie, there are no CRLFs in
 * the encoded string. Methods are synchronized to be thread safe.
 */
public class Base64Codec extends AbstractPreferences {

	private String store;
	
	private static Base64Codec instance = new Base64Codec();

	private Base64Codec() {
		super(null, "");
	}

	/**
	 * Returns the Base64 representation of the specified byte array.
	 * 
	 * @param b The byte array to convert.
	 * @return The Base64 representation of the specified byte array.
	 */
	public static synchronized String encode(byte[] b) {
		instance.putByteArray(null, b);
		return instance.get(null, null);
	}

	/**
	 * Converts the specified Base64 string to the corresponding byte array.
	 * 
	 * @param base64String
	 * @return The specified Base64 string as byte array, <b>not</b> <tt>null</tt>.
     * @throws IllegalArgumentException if <tt>base64String</tt> is 
     *         not a valid Base64 string.
     * @throws NullPointerException if <tt>base64String</tt> is <tt>null</tt>.
	 */
	public static synchronized byte[] decode(String base64String) throws NullPointerException, IllegalArgumentException {
		if (base64String == null)  throw new NullPointerException();
		instance.store = base64String;
		byte[] result = instance.getByteArray(null, null);
		if (result == null) {
			throw new IllegalArgumentException("'" + base64String + "' is not a valid Base64 string.");
		}
		return result;
	}

	@Override
	public String get(String key, String def) {
		return store;
	}

	@Override
	public void put(String key, String value) {
		store = value;
	}
	
	// Not used
	
	@Override
	protected AbstractPreferences childSpi(String name) {
		throw new AssertionError("Should never be reached!");
	}
	
	@Override
	protected void putSpi(String key, String value) {
		throw new AssertionError("Should never be reached!");
	}
	
	@Override
	protected String getSpi(String key) {
		throw new AssertionError("Should never be reached!");
	}
	
	@Override
	protected void removeSpi(String key) {
		throw new AssertionError("Should never be reached!");
	}
	
	@Override
	protected String[] keysSpi() throws BackingStoreException {
		throw new AssertionError("Should never be reached!");
	}
	
	@Override
	protected String[] childrenNamesSpi() throws BackingStoreException {
		throw new AssertionError("Should never be reached!");
	}
	
	@Override
	protected void syncSpi() throws BackingStoreException {
		throw new AssertionError("Should never be reached!");
	}
	
	@Override
	protected void removeNodeSpi() throws BackingStoreException {
		throw new AssertionError("Should never be reached!");
	}
	
	@Override
	protected void flushSpi() throws BackingStoreException {
		throw new AssertionError("Should never be reached!");
	}

}